Self-locking separable seam assembly

ABSTRACT

A self-locking separable seam assembly comprising a pair of identical extruded semi-rigid strips of plastic material having a tubular portion tear-drop shape in cross section along one lateral edge of the mounting web thereof. One sidewall of the tubular portion is slotted to permit these overlapped edges to be pressed into interlocking engagement with one edge of each slot closely spaced from the exterior of the tubular portion of the other strip and cooperating therewith to lock the closed seam against disassembly.

[ 1 Jan. 7, 1975 FOREIGN PATENTS OR APPLICATIONS SELF-LOCKING SEPARABLE SEAM ASSEMBLY 24/201 C 'Belgium................ 24/201 C .m m n S U A 41 65 99 NH 11 I 51:1 0 2. 50 25 s k a 0 6n (4J3 3m e o s a F! D l Pe .05 Am m e W r WC O t n e V n I l 6 l France Calif.

[22] Filed: Dec. 5, 1973 [21] Appl. No.: 421,847

Primary Examiner-Bernard A. Gelak Attorney, Agent, or FirmSe1lers and Brace 24/201 C, 24/201 HH, 138/168 [57] ABSTRACT A self-locking separable seam assembly comprising a Int. A441) 17/00 pair of identical extruded semi-rigid strips of plastic material having a tubular portion tear-drop shape in cross section along one lateral edge of the mounting web thereof. One sidewall of the tubular portion is t 700 2 36 2 W6 H36 H11 C 20 ,2 WE H R 0 M2 R m0 3 2 NS m5 S0 f3 0 M4 2 .1 F l 8 5 l [56] Refuences Cited slotted to permit these overlapped edges to be pressed UNITED STATES PATENTS into interlocking engagementwith one edge of each 24/201 C slot closely'spaced from the exterior of the tubular 24 201 3 portion of the other strip and cooperating therewith to 24/237 lock the closed seam against disassembly.

Sipe....... 2,756,172 7/1956 Kidd.. 2,787,435 4/1957 Shields... 2,909,822 10/1959 3,638,286 2/1972 9 Claims, 4 Drawing Figures SELF-LOCKING SEPARABLE SEAM ASSEMBLY This invention relates to interlocking seam assemblies, and more particularly to an improved separable seam assembly designed for assembly by overlapping portions of each strip and applying pressure until the parts snap into assembled position and including a relatively rigid locking rib strongly resisting disassembly.

There are a great variety of separable seam assemblies formed from extruded plastic material relying upon many different operating principles to hold the parts assembled. Some of these require advancing tools or slider devices progressively along the seam to bring the parts into or out of interlocking engagement. Others are designed to be assembled without the use of clo sure devices. Most of these assemblies require the use of relatively supple flexible elastomeric material either because such material is essential to the assembly and disassembly of the seam or because the operating environment requires an easily flexed seam. A serious shortcoming of such assemblies resides in the fact that they are subject to unpredictable and premature complete or partial disassembly. Once one portion of the seam opens, the stress or loading action on the remainder of the seam readily effects its opening.

Proposals have been made for seam constructions which interlock with snap action and resist disassembly so long as a load is applied in the general plane of the seam and in a direction serving to hold the parts assembled. However, if this force is relaxed or reversed, the seam is subject to opening and disassembly contrary to the users intentions.

An illustrative example of an operating environment having need for an easily assembled seam and which strongly resists opening is one in which an appearance jacket is employed to hold insulation or the like assembled about ducts and conduits. The insulation material may be formed in one or more parts appropriately tailored to encompass the duct work following which an appearance jacket of impervious material is applied to hold the parts firmly in place. The seam employed to hold such a jacket assembled desirably interlocks with a press fit and a minimum of effort and manipulation without risk of disassembly.

A seam designed for this purpose and which has been quite satisfactory is disclosed in Eichberg US. Pat. No. 3,638,286 granted Feb. 1, 1972. However, a shortcoming of that construction is that it includes inadequate means safeguarding against disassembly if slight disassembly forces are applied to the two seam members. Eichberg U.S. Pat. No. 3,495,306 granted Feb. 17, 1970 discloses another suitable seam but opens even more readily and easily than does the first mentioned Eichberg construction.

With the foregoing and other shortcomings of the prior art in mind, the present invention has as its primary purpose the provision of an improved separable seam assembly formed from two identical strips of plastic material readily assembled when overlapped and pressed toward one another and additionally includes locking means cooperating strongly to resist separation of the seam unless manipulated in a particular manner. These objectives are accomplished by using semi-rigid plastic material, one lateral edge of the mounting web of which is provided with a tubular portion of slotted tear-drop configuration. One sidewall of the tear-drop is slotted or cut away lengthwise of the tear-drop to form an entrance passage for one lip edge of the slot in the other seam part. The other lip edge of each slot is positioned to lie in direct abutment with the exterior bottom portion of the other seam member when the parts are assembled thereby forming a locking rib effective to block disassembly of the seam. The locking rib thereby provided on each strip is positioned so as to be placed in compression upon the application of forces acting in the plane of the seam in a direction tending to open the seam. This locking rib must be deflected in a direction normal to the plane of the seam before it is possible to separate the seam parts. By judicious application of these design principles there is provided a new and improved self-locking seam having many advantages lacking in any prior seam construction.

It is therefore a primary object of the present invention to provide an improved self-locking separable seam assembly formed from identical extruded strips of elastomeric material.

Another object of the invention isthe provision of a separable seam assembly in which identical elongated seam members are readily pressable into interlocking engagement and including locking rib means strongly resisting disassembly of the seam.

Another object of the invention is the provision of an interlocking seam assembly comprising identical strips having a tear-drop shaped tubular portion along one lateral edge slotted lengthwise of one side thereof thereby to permit the overlapped tubular edges to be pressed together by application of slight pressure.

These and other more specific objects will appear upon reading the following specification and claims and upon considering in connection therewith the attached drawing to which they relate.

Referring now to the drawing in which a preferred embodiment of the invention is illustrated:

FIG. 1 is a perspective view of an illustrative embodiment of the invention separable seam mounted on an appearance jacket and shown assembled about heat insulation embracing a tubular duct;

FIG. 2 is a cross-sectional view on an enlarged scale taken along line 22 on FIG. 1;

FIG. 3 is a view similar to FIG. 2 but showing the scam in the process of being pressed into assembled position; and

FIG. 4 is an end view on an enlarged scale of one'of the two seam parts.

Referring initially to FIG. 1, there is shown an illustrative embodiment to the invention self-locking seam assembly, designated generally 10, assembled to the opposite lateral edges of an impervious supple plastic appearance jacket 11. Jacket 11 is wrapped snugly about one or more pieces of heat insulation 12 appropriately shaped to snugly embrace a conduit or duct 13 employed to conduct either a hot or a cold fluid.

Seam assembly 10 comprises a pair of identical plastic strips 15,15 preferably extruded from suitable plastic material, such as polyvinyl chloride, or the like, compounded to have a shore hardness of approximately on the A scale. Each strip includes a wide mounting web 16,16 adapted to be suitably secured, as by heat fusion, to the edge of material desired to be equipped with a seam, such as the insulation enclosure and appearance jacket 11. The other lateral edge of each strip may be appropriately described as of .l-shape and includes a stern portion 17,17 integral with a trough-shaped return bend portion 18,18 of crescent shape with the mid-portion of substantially greater thickness than its opposite edges. Alternatively, the lateral edge portion of strips 15,15 may be described as of generally tubular configuration and more specifically as tear-drop shape in cross-section. One sidewall of the tear'drop is slotted from end to end to provide an entrance slot having a width approximating or slightly exceeding the thickest portion of the trough portion. The remainder of the slotted sidewall comprises a relatively rigid but deflectable locking rib 21 located substantially opposite lip portion 22 of trough 18. For this reason it will be evident that the locking rib must be deflected inwardly toward sidewall 17 to permit internesting assembly of the two trough-shaped portions 18,18.

The assembly of appearance jacket 11 about the pieces of insulation material 12 is accomplished quickly and expeditiously simply by wrapping the supple appearance jacket about the insulation and compressing the latter sufficiently to permit the seam strips 15,15 to be pulled into the overlapping relationship illustrated in FIG. 3 with the lip edges 22,22 in close juxtapositionL While so held, the tubular portion of the outer strip is pressed inwardly causing each of the locking ribs 21,21 to be deflected inwardly toward the opposite sidewall 17,17. The radial pressure then being applied against the outer one of the strips is released as the hoop tension then acting on the appearance jacket acts to pull the two trough shaped members into internested assembled relation, as shown in FIG. 2. As this occurs, the locking ribs 21,21 are free to return to their normal relaxed condition with snap action owing to the semi-rigidity of the plastic material from which the two seam strips are formed. The free edges of the locking ribs then lie closely against the exterior of the bottom of the trough-shaped portions and are highly effective to resist and prevent separation of the seam parts for self-obvious reasons.

The closed seam can be reopened if there be need. This is preferably initiated from one end of the closed seam by depressing locking rib 21' inwardly while at the same time applying pressure to the other side of the seam in a direction to disengage its troughshaped portion 18, past the depressed locking rib 21 Once an end portion of the seam has been opened in this manner, it is a simple matter to progressively open the remainder of the seam.

While the particular self-locking separable seam assembly herein shown and disclosed in detail is fully capable of attaining the objects and providing the advantages hereinbefore stated, it is to be understood that is is merely illustrative of the presently preferred embodiment of the invention and that no limitations are intended to the detail of construction or design herein shown other than as defined in the appended claims.

I claim:

1. An interlocked self-locking separable seam assembly comprising a pair of generally J-shaped semi-rigid continuous strips of identical cross-section extruded from plastic material and including a trough-shaped portion integral with a stern portion, said troughshaped portion having a free lip edge extending therealong, a semi-rigid deflectable locking rib integral with said stem portion and extending lengthwise of said strip with the free edge thereof extending toward and closely spaced from the lip edge of said trough-shaped portion, said locking rib being so positioned as to require deflection toward said stem portion as said trough-shaped portions of said strips are overlapped and pressed into interlocking engagement with one another. and the free edges of said locking ribs then resuming the initial unstressed position thereof and cooperating with the juxtaposed exterior surfaces of said cup-shaped portions to resist separation of said interlocked strips.

2. A seam assembly as defined in claim 1 characterized in that the bottom of said trough-shaped portion is substantially thicker than the free lip edge thereof.

3. A seam assembly as defined in claim 1 characterized in that the bottom of said trough-shaped portion is substantially thicker and stiffer than said stem portion.

4. A seam assembly as defined in claim 1 characterized in that the spacing between the free edge of said locking rib and the juxtaposed exterior surface of said trough-shaped portion approximates the wall thickness of said trough-shaped portion.

5. A seam assembly as defined in claim 1 characterized in that said strips have a shore hardness of the order of on the A scale. a

6. An interlocked self-locking separable seam assembly comprising a pair of semi-rigid strips of identical cross-section extruded from plastic material, said strips having a wide thin mounting web formed along one lateral edge with a tubular portion of tear-drop shape in cross-section, the midportion of one sidewall of said tubular portion having a narrow endless slot extending lengthwise from end to end thereof to permit interlocking assembly of said pair of strips when said tear drop portions are overlapped with the slots of each in juxtaposition and positioned for interlocking nesting engagement with one another.

7. A seam assembly as defined in claim 6 characterized in that said slot has a width approximating the wall thickness of the bottom portion of said tear-drop shaped portion.

8. A seam assembly as defined in claim 6 characterized in that the wall of said tubular portion remote from said mounting web is crescent-shaped in cross-section and substantially thicker along the midlength thereof than along the opposite sides of said thick midlength portion.

9. A seam assembly as defined in claim 6 characterized in that the walls of said tubular portions integral with the adjacent portion of said mounting web are rel-- atively thin and more flexible than the relatively thick and relatively rigid portion of said tubular portion remote from said mounting web. 

1. An interlocked self-locking separable seam assembly comprising a pair of generally J-shaped semi-rigid continuous strips of identical cross-section extruded from plastic material and including a trough-shaped portion integral with a stem portion, said trough-shaped portion having a free lip edge extending therealong, a semi-rigid deflectable locking rib integral with said stem portion and extending lengthwise of said strip with the free edge thereof extending toward and closely spaced from the lip edge of said trough-shaped portion, said locking rib being so positioned as to require deflection toward said stem portion as said trough-shaped portions of said strips are overlapped and pressed into interlocking engagement with one another, and the free edges of said locking ribs then resuming the initial unstressed position thereof and cooperating with the juxtaposed exterior surfaces of said cup-shaped portions to resist separation of said interlocked strips.
 2. A seam assembly as defined in claim 1 characterized in that the bottom of said trough-shaped portion is substantially thicker than the free lip edge thereof.
 3. A seam assembly as defined in claim 1 characterized in that the bottom of said trough-shaped portion is substantially thicker and stiffer than said stem portion.
 4. A seam assembly as defined in claim 1 characterized in that the spacing between the free edge of said locking rib and the juxtaposed exterior surface of said trough-shaped portion approximates the wall thickness of said trough-shaped portion.
 5. A seam assembly as defined in claim 1 characterized in that said strips have a shore hardness of the order of 95 on the A scale.
 6. An interlocked self-locking separable seam assembly comprising a pair of semi-rigid strips of identical cross-section extruded from plastic material, said strips having a wide thin mounting web formed along one lateral edge with a tubular portion of tear-drop shape in cross-section, the midportion of one sidewall of said tubular portion having a narrow endless slot extending lengthwise from end to end thereof to permit interlocking assembly of said pair of strips when said tear drop portions are overlapped with the slots of each in juxtaposition and positioned for interlocking nesting engagement with one another.
 7. A seam assembly as defined in claim 6 characterized in that said slot has a width approximating the wall thickness of the bottom portion of said tear-drop shaped portion.
 8. A seam assembly as defined in claim 6 characterized in that the wall of said tubular portion remote from said mounting web is crescent-shaped in cross-section and substantially thicker along the midlength thereof than along the opposite sides of said thick midlength portion.
 9. A seam assembly as defined in claim 6 characterized in that the walls of said tubular portions integral with the adjacent portion of said mounting web are relatively thin and more flexible than the relatively thick and relatively rigid portion of said tubular portion remote from said mounting web. 